In the prior art, methods are known for preparing weakly or strongly superalkalinized sulfonates from sulfonic acids obtained by the sulfonation of different alkylaryl hydrocarbons and from an excess of alkaline earth base. The alkylaryl hydrocarbons subjected to the sulfonation reaction are obtained by alkylation via the Friedel-Crafts reaction of different aryl hydrocarbons, particularly aromatic hydrocarbons, with two different types of olefin. The first type of olefins are branched olefins obtained by the oligo-polymerization of propylene to C15 to C24 hydrocarbons, particularly the propylene tetrapolymer dimerized to a C24 olefin. The second type are linear olefins obtained by the oligo-polymerization of ethylene to C14 to C40 hydrocarbons.
It is easy to obtain a good dispersion in the medium of the alkaline earth base not fixed in the form of salt if the alkylaryl sulfonic acid is derived from a hydrocarbon obtained by alkylation of an aryl hydrocarbon with a branched olefin. However, dispersion is particularly difficult when a high percentage of the alkylaryl hydrocarbon has the aryl substituent on positions 1 or 2 of a linear alkyl chain, due to the formation of a skin when exposed to open air. This poor dispersion is especially pronounced if the medium also contains a high proportion of sulfonate, that is, if it corresponds to a low Base Number (between 3 and 60), hence to a low content of free lime and the absence of carbon dioxide and carbonate.
In fact, during the alkylation reaction with benzene or another aromatic or aryl hydrocarbon and a linear olefin, 25 mole % of the alkylaryl hydrocarbon has the aryl substituent on positions 1 or 2 of the linear alkyl chain. Traditionally, aromatics attached at the 2-position of the alkyl group give the most absorption of water. When prepared by the method described, for example in French Patent No. 2,564,830, this high proportion of alkylaryl hydrocarbon having an aryl radical on position 1 or 2 of the linear alkyl chain results in a sulfonate that exhibits hygroscopic properties such that a superficial xe2x80x98skinxe2x80x99 is formed. This xe2x80x98skinxe2x80x99 makes this product unacceptable as an additive for lubricating oil. Furthermore, the formation of this superficial skin is generally accompanied by a very low filtration rate, a high viscosity, a low incorporation of calcium, a deterioration of anti-rust performance, and an undesirable turbid appearance, or even sedimentation, when the sulfonate thus prepared is added at the rate of 10% by weight to a standard lubricating oil and stored for examination.
Chromatographic analysis has been conducted to identify each of the different isomers differing by the position of the aryl radical on the carbon atom of the linear alkyl chain, and their respective influence on the properties of the corresponding alkylaryl sulfonates of alkaline earth obtained from these different isomers has been examined. It was thus discovered that the aforementioned drawbacks could be overcome, inasmuch as the mole % of the aryl hydrocarbon, other than benzene, having the aryl substituent on positions 1 or 2 of the linear alkyl chain was between 0 and 13%, and preferably between 5 and 11%, and more particularly between 7 and 10%. This discovery was the subject of U. S. Pat. No. 5,939,594, issued Aug. 17, 1999 to Le Coent.
However, satisfactory results had not been obtained when the aryl hydrocarbon was benzene. Skin formation occurred with the use of benzene, even if the benzene was alkylated with a very long chain linear mono olefin so that the mole % of the aryl hydrocarbon having the aryl substituent on positions 1 or 2 of the linear alkyl chain was between 0 and 13%, and preferably between 5 and 11%, and more particularly between 7 and 10%.
French Patent Application No. 96/10,833 discloses that the aforementioned drawbacks could be overcome by using a mixture of alkylaryl sulfonates of superalkalinized alkaline earth metals comprising:
(a) from 50% to 85% of a linear mono-alkyl phenyl sulfonate in which the linear alkyl chain contains between 14 and 40 carbon atoms, and between 0 and 13 mole % of the phenyl sulfonate radical of the alkaline earth metal is fixed on position 1 or 2 of the linear alkyl chain, and
(b) from 15% to 50% of a heavy alkylaryl sulfonate selected from:
(i) dialkylaryl sulfonates wherein both alkyl substituents are linear alkyl chains, of which the sum of the carbon atoms is from 16 to 40, or
(ii) mono or polyalkylaryl sulfonates wherein the alkyl substituent or substituents are branched chains, wherein the sum of the carbon atoms is from 15 to 48 carbon atoms.
This mixture of alkylaryl sulfonates has a maximum of 10 mole % of the phenyl sulfonate radical of the alkaline earth metal fixed on position 1 or 2 of the linear alkyl chain. This mixture has no skin formation after three days of storage in an open jar at room temperature. It has good calcium incorporation, a low viscosity, good solubility, and good performance.
European Patent Application No. 98401968.7 discloses a mixture of alkyl phenyl sulfonates of alkaline earth metals having low color and no skin formation even after three days of storage in an open jar at room temperature. That mixture comprises:
(a) from 20% to 70% of a linear mono-alkylphenyl sulfonate in which the linear mono-alkyl substituent contains from 14 to 40 carbon atoms and the mole % of the phenyl sulfonate radical fixed on position 1 or 2 of the linear alkyl chain is between 10% and 25%, and,
(b) from 30% to 80% of a branched mono-alkylphenyl sulfonate in which the branched mono alkyl substituent contains from 14 to 18 carbon atoms.
The present invention provides an alkylaryl composition wherein the aryl radical is other than phenol and wherein the alkyl radical is derived from an isomerized C14 to C40 normal alpha olefin and wherein either (1) the weight percent of the aryl radical fixed at position 1 or 2 of a linear alkyl chain is less than about 23, or (2) at least 28 weight percent of the alkyl radicals are branched chain alkyl radicals, or (3) both.
Further provided in accordance with this invention is an alkaline earth alkylaryl sulfonate having a Base Number of at least 250, where the aryl radical is other than phenol, wherein the alkyl radical is derived from An isomerized C14 to C40 normal alpha olefin and wherein either (1) the weight percent of the aryl sulfonate radical fixed at position 1 or 2 of a linear alkyl chain is less than about 23, or (2) at least 28 weight percent of the alkyl radicals are branched chain alkyl radicals, or (3) both.
Also provided in accordance with this invention is an alkaline earth alkylaryl sulfonate having a Base Number of about 2 to about 60, where the aryl radical is other than phenol, wherein the alkyl radical is derived from an isomerized C14 to C40 normal alpha olefin and wherein either (1) the weight percent of the aryl sulfonate radical fixed at position 1 or 2 of a linear alkyl chain is less than about 23, or (2) at least 28 weight percent of the alkyl radicals are branched chain alkyl radicals, or (3) both.
The present invention also provides a lubricating oil composition comprising a lubricating oil and an alkaline earth alkylaryl sulfonate having a Base Number of at least 250, where the aryl radical is other than phenol, wherein the alkyl radical is derived from an isomerized C14 to C40 normal alpha olefin and wherein either (1) the weight percent of the aryl sulfonate radical fixed at position 1 or 2 of a linear alkyl chain is less than about 23, or (2) at least 28 weight percent of the alkyl radicals are branched chain alkyl radicals, or (3) both.
Further provided in accordance with this invention is a lubricating oil composition comprising a lubricating oil and an alkaline earth alkylaryl sulfonate having a Base Number of about 2 to about 60, where the aryl radical is other than phenol, wherein the alkyl radical is derived from an isomerized C14 to C40 normal alpha olefin and wherein either (1) the weight percent of the aryl sulfonate radical fixed at position 1 or 2 of a linear alkyl chain is less than about 23, or (2) at least 28 weight percent of the alkyl radicals are branched chain alkyl radicals, or (3) both.
The present invention also provides a concentrate comprising from about 0.5 wt. % to about 90 wt. % of an alkaline earth alkylaryl sulfonate having a Base Number of at least 250, where the aryl radical is other than phenol, wherein the alkyl radical is derived from an isomerized C14 to C40 normal alpha olefin and wherein either (1) the weight percent of the aryl sulfonate radical fixed at position 1 or 2 of a linear alkyl chain is less than about 23, or (2) at least 28 weight percent of the alkyl radicals are branched chain radicals, or (3) both, the balance of the concentrate being an organic liquid diluent compatible with the alkaline earth alkylaryl sulfonate.
Also provided by the present invention is a concentrate comprising from about 0.5 wt. % to about 90 wt. % of an alkaline earth alkylaryl sulfonate having a Base Number of about 2 to about 60, where the aryl radical is other than phenol, wherein the alkyl radical is derived from an isomerized C14 to C40 normal alpha olefin and wherein either (1) the weight percent of the aryl sulfonate radical fixed at position 1 or 2 of a linear alkyl chain is less than about 23, or (2) at least 28 weight percent of the alkyl radicals are branched chain radicals, or (3) both, the balance of the concentrate being an organic liquid diluent compatible with the alkaline earth alkylaryl sulfonate.
The present invention provides from the same alkylate both a high overbased (xe2x80x9cHOBxe2x80x9d; BN higher than 250) alkaline earth alkylaryl sulfonate having improved compatibility and solubility, and a low overbased (xe2x80x9cLOBxe2x80x9d; BN from 2 to 60) alkaline earth alkylaryl sulfonate having good solubility while having low color and no skin formation.
While we have found that a too high concentration of 1 -aryl or 2-aryl linear alkylaryl sulfonate causes skin formation in LOB sulfonates, we have found that the higher BN (at least 250 BN) sulfonates are less sensitive to 2-aryl content in the alkylate because the 2-aryl content is diluted by the salts. Therefore, if the BN is high enough (at least 250), and the aryl radical is not phenol, then the weight % of the aryl-sulfonate radical fixed on position 1 or 2 of the linear alkyl chain can be between 2% and 23% (preferably between 13% and 23%) without any skin forming. This high weight percentage of 2-aryl gives a sulfonate having good water absorption properties.
The alkyl chain of the alkaline earth alkylaryl sulfonates of the present invention contains between 14 and 40 carbon atoms, preferably from 20 to 24 carbon atoms.
Some of the alkyl chains of the alkylaryl or alkylaryl sulfonate compositions may be branched. Preferably, at least 28 weight percent, more preferably at least 30 weight percent, of the alkyl radicals are branched chain radicals.
Preferably, the alkaline earth alkylaryl sulfonates of this invention have a mono-alkylate content of at least 87% and an Iodine number of less than 1.0.
Preferably, the alkaline earth alkylaryl sulfonates of this invention are derived from an isomerized C14-C40 normal alpha olefin, more preferably from isomerized C20-C24 normal alpha olefin.
The alkaline earth alkylaryl sulfonates of the present invention are preferably derived from an alkylate formed by the reaction of benzene and isomerized normal alpha olefins in the presence of hydrogen fluoride, preferably in a one-stage reactor. Preferably the sulfonate is formed in the presence of methanol and xylene, but preferably in the absence of chlorine (if BN higher than 250).
For BN between 2 and 60 the process used is described in U.S. Pat. No. 4,764,295, issued Aug. 16, 1988 to Le Coent entitled Non-Foaming Detergent-Dispersant Additives for Lubricating Oils and Process for Making Such Additives, which is incorporated by reference herein in its entirety.
A way has been found to have a single alkylation for sulfonates by starting from the same normal alpha olefin having 14 to 40 carbon atoms, preferably from 20 to 24 carbon atoms. Whatever the BN is (from 3 to 500), the following route is used:
(a) Isomerization of NAO C14-C40, preferably C20-C24. 
At least two types of acidic catalysts can be used for isomerization. The acidic catalyst can be solid or liquid. Preferably, the first type of acidic catalyst is a solid catalyst having at least one metal oxide and having an average pore size of less than 5.5 angstroms. More preferably, it is a molecular sieve with a one-dimensional pore system, such as SM-3, MAPO-11, SAPO-11, SSZ-32, ZSM-23, MAPO-39, SAPO-39, ZSM-22 and SSZ-20. Other possible solid acidic catalysts useful for isomerization include ZSM-35, SUZ4, NU-23, NU-87 and natural or synthetic ferrierites. These molecular sieves are well-known in the art and are discussed in Rosemarie Szostak""s Handbook of Molecular Sieves (New York, Van Nostrand Reinhold, 1992) and in U.S. Pat. No. 5,282,858, which is hereby incorporated by reference for all purposes. Another type of isomerization catalyst that can be used is iron pentacarbonyl (Fe(CO)5).
The isomerization process may be carried out in batch or continuous mode. The process temperatures can range from 50xc2x0 C. to 250xc2x0 C. In the batch mode, a typical method is to use a stirred autoclave or glass flask, which may be heated to the desired reaction temperature. A continuous process is most efficiently carried out in a fixed bed process. Space rates in a fixed bed process can range from 0.1 to 10 or more WHSV. In a fixed bed process, the catalyst is charged to the reactor and activated or dried at a temperature of at least 150xc2x0 C. under vacuum or flowing inert, dry gas. After activation, the catalyst is cooled to the desired reaction temperature and a flow of the olefin is introduced. The reactor effluent containing the partially branched, isomerized olefin is collected. The resulting partially-branched isomerized olefin contains a different olefin distribution (alpha-olefin, beta-olefin, internal-olefin, trisubstituted olefin and vinylidene-olefin) and branching content than the un-isomerized olefin and conditions are chosen in order to obtain the appropriate structure regarding the level of double bonds between carbon 1 and carbon 2 of the alkyl chain of the olefin (alpha-olefin content).
The appropriate olefin derived from the NAO has less than 15 weight percent alpha content, preferably between 0 and 8 weight percent, with at least 25 weight percent, preferably about 29 to about 60 weight percent of the olefins being branched.
(b) Alkylation
Two routes can be used:
1. Alkylation with HF as a Catalyst
One reactor and a high charge molar ratio benzene/olefin, typically about 10, are used in order to increase the alkylation rate versus isomerization and dimerization rate. The resulting alkylate has a low iodine number and a high level of monoalkylbenzene. As a consequence, a high level of sulfonation can be achieved, leading to an LOB sulfonate (BN between 2 and 60) with no skin formation if stored in an open jar, low viscosity, low color, good solubility, fast rate of filtration and good stability at high temperature. It should be noted in particular that another alkylate (branched or linear dialkyl) is not required to avoid skin formation on the corresponding LOB sulfonates of this invention. Moreover, such an alkylate leads to high overbased sulfonates (at least 250 BN) having good solubility and other properties.
2. Alkylation Using a Solid Acidic Alkylation Catalyst
The alkylation catalyst is a solid catalyst that has at least one metal oxide, which is selected from the group consisting of natural zeolites, synthetic zeolite, synthetic molecular sieves and clays. Preferably, the solid acidic catalyst comprises the acid forms of an acidic clay, or an acidic molecular sieve or a zeolite having an average pore size of at least 6.0 angstroms. Such zeolites include zeolite Y, beta, SSZ-25, SSZ-26 and SSZ-33. Other possible catalysts include L zeolite, mordenite, boggsite, cloverite. VPI-5, MCM-41, MCM-36, SAPO-8, SAPO-5, MAPO-36, SAPO-40, SAPO-41, MAPSO-46, CoAPO-50, hexagonal faujasite, ECM-2, gmelinite, mazzite (omega zeolite), offretite, ZSM-18 and ZSM-12. These catalysts are discussed in Rosemarie Szostak""s Handbook of Molecular Sieves (New York, Van Nostrand Reinhold, 1992). More preferably, the solid acidic catalyst comprises zeolite Y. A preferred zeolite Y has a silica to alumina ratio of at least 40:1.
Useful acidic clays may be derived from naturally occurring or synthetic materials. One skilled in the art would realize that there are a number of such clays that are known to be alkylation catalysts. Examples of such acidic clays include montmorillonite, laponite and saponite. Pillared clays may also be used as catalysts.
The alkylation reaction is typically carried out with an aromatic and an olefin in molar ratios from 1:15 to 25:1. The process temperatures can range from 100xc2x0 C. to 250xc2x0 C. As the olefins have a high boiling point, the process is preferably carried out in the liquid phase. The alkylation process may be carried out in batch or continuous mode. In the batch mode, a typical method is to use a stirred autoclave or glass flask which may be heated to the desired reaction temperature. A continuous process is most efficiently carried out in a fixed bed process. Space rates in a fixed bed process can range from 0.1 to 10 or more WHSV. In a fixed bed process, the catalyst is charged to the reactor and activated or dried at a temperature of at least 150xc2x0 C. under vacuum or flowing inert dry, gas. After activation, the catalyst is cooled to the desired reaction temperature and a flow of the aromatic compound is introduced. Pressure is increased by means of a back pressure valve so that the pressure is above the bubble point pressure of the feed composition at the desired reaction temperature. After pressurizing the system to the desired pressure, the temperature is increased to the desired reaction temperature. Optionally, the aromatic may be added to the catalyst at reaction temperature. A flow of the olefin is then mixed with the aromatic and allowed to flow over the catalyst. The reactor effluent containing alkylate product and excess aromatic is collected. Excess aromatic is then removed by distillation, stripping evaporation under vacuum or other means know to those skilled in the art.
In its broadest aspect, the present invention involves an alkylaryl composition, an alkaline earth alkylaryl sulfonate, methods for its preparation, and its application as a detergent/dispersant additive for lubricating oils.
Prior to discussing the invention in further detail, the following terms will be defined:
DEFINITIONS
As used herein the following terms have the following meanings unless expressly stated to the contrary:
The term xe2x80x9calkylaryl compositionxe2x80x9d refers to a hydrocarbon or mixture of hydrocarbons each comprising an aryl group, such as benzyl, tolyl, or ortho-xylyl having attached directly to it one or more C14 to C40 alkyl groups.
The term xe2x80x9calkaline earth metalxe2x80x9d refers to calcium, barium, magnesium and strontium.
The term xe2x80x9calkaline earth alkylaryl sulfonatexe2x80x9d refers to an alkaline earth metal salt of an alkylaryl sulfonic acid. In other words, it is an alkaline earth metal salt of an aryl that is substituted with (1) an alkyl group and (2) a sulfonic acid group that is capable of forming a metal salt.
The term xe2x80x9cthe weight % of the aryl sulfonate radical on position 1 or 2 of a linear alkyl chainxe2x80x9d refers to the weight percentage of all the aryl sulfonate radicals fixed on a linear alkyl chain that are fixed at the first or second position of the linear alkyl chain. The first position of the linear alkyl chain is the position at the end of the chain. The second position of the linear alkyl chain is the position immediately next to the first position.
The term xe2x80x9c1 -arylxe2x80x9d refers to an aryl sulfonate radical fixed on a linear alkyl chain at the first position of the linear alkyl chain.
The term xe2x80x9c2-arylxe2x80x9d refers to an aryl sulfonate radical fixed on a linear alkyl chain at the second position of the linear alkyl chain.
The term xe2x80x9cmonoalkylate contentxe2x80x9d is the weight percentage of the alkylate that is not dialkylate (100xc3x97monoalkylate/(monoalkylate+dialkylate)).
The term xe2x80x9cIodine Numberxe2x80x9d is the absorption value (Hxc3xcbl Number or Wijs number), which is the quantity of iodine, in grams, absorbed by 100 grams of fat or oil under specified conditions. It indicates the amount of double bonds present.
The term xe2x80x9cBase Numberxe2x80x9d or xe2x80x9cBNxe2x80x9d refers to the amount of base equivalent to milligrams of KOH in one gram of sample. Thus, higher BN numbers reflect more alkaline products, and therefore a greater alkalinity reserve. The BN of sample can be determined by ASTM Test No. D2896 or any other equivalent procedure.
The term xe2x80x9coverbased alkaline earth alkylaryl sulfonatexe2x80x9d refers to a composition comprising a diluent (e.g., lubricating oil) and an alkylaryl sulfonate wherein additional alkalinity is provided by a stoichiometric excess of an alkaline earth metal base, based on the amount required to react with the acidic moiety of the sulfonate. Enough diluent should be incorporated in the overbased sulfonate to ensure easy handling at safe operating temperatures.
The term xe2x80x9clow overbased alkylaryl sulfonatexe2x80x9d refers to an overbased alkaline earth alkylaryl sulfonate having a BN of about 2 to about 60.
The term xe2x80x9chigh overbased alkaline earth sulfonatexe2x80x9d refers to an overbased alkaline earth alkylaryl sulfonate having a BN of 250 or more. Generally a carbon dioxide treatment is required to obtain high BN overbased detergent compositions. It is believed that this forms a colloidal dispersion of metal base.
Unless otherwise specified, all percentages are in weight percent, all ratios are molar ratios, and all molecular weights are number average molecular weights.
ALKYLARYL COMPOSITION
The alkylaryl composition (or xe2x80x9calkylatexe2x80x9d) can be formed by the reaction of an aryl compound, such as benzene or toluene, and isomerized, normal alpha olefin in the presence of hydrogen fluoride, preferably in a one-stage reactor.
ALKYLARYL SULFONATES
The alkylaryl sulfonates of the present invention are high or low overbased alkaline earth alkylaryl sulfonates having linear alkyl groups. These alkylaryl sulfonates have improved compatibility and solubility, while having low color and no skin formation.
The alkylaryl sulfonates are high overbased (BN of at least 250), or low overbased sulfonates (BN from 2 to 60xe2x80x94preferably from 5 to 30).
It is also essential that the aryl radical is not phenol, since high overbased alkylphenoxy sulfonates having 2-aryl content tend to be too viscous for easy handling. Preferably, it is an alkyl benzene sulfonate or an alkyl toluene sulfonate.
The linear alkyl chain contains between 14 and 40 carbon atoms, preferably from 20 to 24 carbon atoms. Preferably, the alkaline earth alkylaryl sulfonate is derived from an isomerized C14-C40 normal alpha olefin, more preferably from an isomerized C20-C24 normal alpha olefin.
Preferably, the alkaline earth alkylaryl sulfonate has a monoalkylate content of at least 87% and an iodine number of less than 1.0.
Aforementioned U.S. Pat. No. 4,764,295 describes alkylaryl sulfonates of alkaline earth metals resulting from alkylation by a linear olefin.
Preferably, the highly overbased alkaline earth alkylaryl sulfonate is formed in the presence of methanol and xylene, and in the absence of chlorine. The process for preparing low overbased alkaline earth alkylaryl sulfonates is described in aforementioned U.S. Pat. No. 4,764,295.
Preferably, the alkaline earth alkylaryl sulfonate is used in a lubricant in conjunction with another detergent, preferably a sulfurized alkaline earth alkylaryl phenate.